Xyzzy wrote:
This has me baffled.
snip
I ride 99% of the time in the small ring. I can only think of 3 or 4
times, since I bought the bike, where I have used the big ring. I would
expect the small ring to wear out long before the large ring. I would
also expect the cassette to show significant wear before the chain
rings, and I definitely wouldn't expect to see wear in just a few
months. I have seen chain rings that are worn to nubs that still worked
fine.
snip

Just to be sure I'm reading you right, is it correct thayt:
1. the bike was bought new
2. there's about 4000 miles on the bike total
3. you haven't changed the chain or rings since new
?

It might just be the photo, but the large ring looks fairly tired -
there does appear to be some pronounced hooking on the teeth.
I know this doesn't tie in with what you said about milage etc., it jut
looks that way in the photo. Beats me how it could happen though...

If the teeth are significantly hooked, I'd suggest changing the ring(s)
when changing the chain. I'd also have a good look at the cassette,
and see if all is well there.

I think that the generally accepted wisdom is the more worn components
wear down new components faster than would be the case on all new
components, eg new chain on old rings - accelerated chain wear -
accelerated cassette wear. Everything gets worn down fairly quickly to
the level of the most worn component in the drivetrain.

You might also take the chance to change the tooth count on one or both
of your rings. If, as you say, you only use the large ring very
occasionally, the whole thing might be geared a little high for you,
and a smaller big ring might give you a more usable set of gears
overall.

HTH,

bookieb.